Preparing Calcite replaced Brachiopods

[Ladyofsteel]

Found this lovely piece in Barrington NSW Australia. It has many crinoids, brachiopods and molluscs in it. I'm particularly interested in these white brachiopod specimens. It looks like calcite (I'm too scared to scratch it to check). They are all over the rock and some of them are half filled with calcite showing that it potentially goes really deep. Potentially a full outline of a brachiopod in calcite. What do you guys think? I've included some microscope pictures to help. Also is there a way to prep them out of the matrix? I believe the matrix is limestone. Is there an acid that WONT damage calcite? I do have a dremmel engraver with palaeo tips as well.

Any tips would be very much appreciated

[ClearLake]

Well, if the fossils are calcite and they are in limestone (calcium carbonate) any acid that I'm aware of will eat them both up.  Maybe at slightly different rates, but I doubt enough to preserve one at the expense of the other.  If the fossils were replaced with silica, then you would be in business with acid.  You are best served by doing a scratch test on some portion of the exposed brachiopod.  Mechanical prep is probably your only option, but maybe someone else will have another opinion.  Good luck!

[Fossildude19]

Mechanical prep is the only way I know of to try to get these exposed.